Old House Ground Wire
My house was built in 1956 and during some electrical upgrades, I've noticed this wire running from jbox to jbox. It's about the same gauge as a wire coat hanger. The photo below is after I upgraded to a deeper plastic box so the GFCI would fit easier, but is the purpose of that wire to ground the old metal jbox? And is that different than a green or bare grounding wire now included in romex? My house wires only have a white and black wire.